Corresponding measuring devices are frequently applied in automation and process control technology. Such measuring devices are available from the firm of Endress+Hauser under the marks, LEVELFLEX® and MULTICAP®, which serve primarily to determine and/or to monitor fill level of a medium in a container.
The above described measuring devices are medium-contacting fill level measuring devices, wherein at least one probe element comes directly in contact with the medium to be measured. The measuring probe is constructed of at least one probe element and one probe holding element. The probe element is usually secured via a probe holding element to a process connection, i.e. an opening or a nozzle on the provided container.
In the following references, construction of such measuring probes and the coupling of the measuring signals into these measuring probes are described.
In German Patent, DE 10 2004 060 119 A1, a coupling unit for a time domain reflectometer is disclosed, in the case of which the probe element is connected via a threaded connection with the coupling unit of the measuring probe. This construction has the advantage, that the probe element can be exchanged and mounted on-site.
Other combinations of probe elements with coupling units are shown in U.S. Pat. No. 6,178,817 B1, German Patent DE 100 45 235 A1 and German Patent DE 100 03 941 A1. In the case of this type of measuring probe connections, the probe element is connected with a threaded lug by means of a connecting element outside of the coupling unit in the process space.
The above described measuring probe, screwed connections are applicable also in the case of a measuring device working according to a capacitive or conductive measuring method. In German Patent DE 2003 00 901 U1, a simple measuring probe securement for a capacitive measuring device is described.
In the state of the art, there are different approaches for releasable measuring probe securements. These have, however, the disadvantage, that the probe element can loosen from the measuring probe securement due to vibrations or because of extraordinary forces. If a probe element loosens completely from the securement in the probe coupling unit, measuring is no longer possible. Furthermore, a fallen probe element in a funnel silo, which, most often, has a feed screw or pump in the lower region, can cause a large amount of damage.